Lewis Carroll Quote

If the Letter is to be in answer to another, begin by getting out that other letter and reading it through, in order to refresh your memory, as to what it is you have to answer, and as to your correspondent's present address (otherwise you will be sending your letter to his regular address in London, though he has been careful in writing to give you his Torquay address in full).

Eight or Nine Wise Words About Letter-Writing (1890)